Muffler for internal-combustion engines



H. GIBSON.

TERNAL COM APPLICATlON FILED D OCT. 1,1920- 1,377,472. Patented May 10, 1921.

2 SHEETS-SHEET 1- H. GIBSON.

MUFFLER FOR INTERNAL COMBUSTION ENGINES.

APPLICATION EILED FEB. I4, I918. RENEWED OCT. I. I920.

Patented May 10, 1921.

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17 11 V ATTORN 3 UNITED STA'ILES HAMILTON GIBSON, 0F SEAL HARBOR, MAINE.

MUFFLER FOR INTERNAL-COMBUSTION ENGINES.

Specification of Letters Patent.

Patented May 10, 1921.

Application filed February 14, 1918, Serial No. 217,084.- Renewed October 1, 1920. Serial No. 414,141.

but more especially those used for the propulsion of aeroplanes. As the operative characteristics of the invention are peculiarly useful and applicable to this latter class of engine, it may be considered and described as designed and intended for that specific purpose, although it may obviously be used for other analogous purposes.

It is well known that the use of an ordinary mufller is necessarily attended by a' gines with such devices, as it is essential to derive from the engine every vestige of power which it is capable of developing. There is an objection, however, to the use of aero engines without a muflier, which for military or strategical reasons may become of very great moment, and that is the noise which they make when in flight, and by which their presence, either by night or day, may be detected for long distances.

ecognizing these conditions I have sought to produce an efficient muffler for deadening the sound of the exhaust of the explosive charges in such engines, while at the same time eliminating, or reducing to an inconsequential minimum all back pressure developed by such operation.

To this end I have developed a muffler,

which, aside from its specific construction, more fully set forth in detail hereinafter, is characterized by the presence of a spiral channel or channels around the discharge tube, into which the exhaust ports or apertures open, and in which by the force of the discharges a current of air rotary with respect to the axis of the mufiier is induced in a spiral path or paths with a velocity proportional to the rate or volume of discharge, whereby such rotating air current or currents will by centrifugal action reduce the atmospheric pressure in the space around which they flow and hence at the ports or points of dischargefrom the central discharge tube and hence tend to accelerate rather than impede the egress of such discharges or gases.

I shall describe by reference to theaccompanylng drawings a muffler in one of the specific forms in which I have developed it, and which, I believe to bethe best and most efficient for practical purposes. In the drawing:

Figure 1 is a perspective view of the device.

Fig. 2 is. a vertical central view of the same, and

Fig. 3 is a horizontal cross section.

The letter A designates an outer shee metal casing or shell of substantially funnel shape, secured in any proper manner around the inner and preferably tapering exhaust pipe or tube B. Both ends of the sheet A are open to the air, that through which the exhaust pipe enters being preferably slightly enlarged, as indicated in the drawing to more readily receive a larger amount of air, and the whole shell being gradually enlarged toward its other end and through substantially its entire active length.

The inclosed space or chamber thus formed around the exhaust pipe is divided into a plurality of compartments, two, three or more as conditions of actual use may determine as best for securing given results,

which may encircle at an increasing ang e or pitch the inner tube or exhaust pipe, such compartments being formed by sheet metal walls or partitions C, so designed or constructed throughout their entire length that they shall offer the least possible resistance to the flow of air and gases through the said compartments which they define, and at the same time perform the functions required of them in directing such flow.

The inner cylinder or pipe B is provided with a plurality of exhaust ports or openings D, beginning at a point just beyond the most contracted part of the inclosing shell or funnel A, which permit the free escape of the exhaust gases into the compartments formed by the partitions C, each of such compartments including a proportionate number of such ports. These exhaust ports constituting, in effect, a substantially continuous port, following the spiral partitions C, have a total and individual area which, as will be understood, is proportional to and determined primarily by the nature of the original exhaust.

' necessity rotate about the inner cylinder.

Such rotation thus promoted will lessen by its centrifugal action the atmospheric pressure about the inner cylinder or upon the exhaust ports, and this effect will not decrease as the gases progress toward the outer or larger end of the casingsince, as

the diameter of the casing steadily increases it will allow the gases within to rotate at an increasing radius as they progress and will thus encourage them both farther away from the central exhaust pipe and forward in the device.

Thus it will happen that the exhaust ports will progressively open into the parts of the chambers or compartments where the atmospheric pressure is below normal. That such discharges as occur will be urged out, the direction of their energy as well as the flow of that volume will be forward, so that they will mainta-inas much as possible of their momentum, and produce an increasing pressure upon the outer compartment walls, and speed since they will be urged by centrifugal force to depart as far as possible from the axial center of the system through which they travel.

Each successive port will have the advantage of the rotating motion developed by the preceding port or ports, since it will discharge into a body of gas already in motion, at a point where the effects of centrifugal force, however slight, will have been created.

Once established this rotary motion of the forward moving gases will tend to draw through the open forward or starting ends of the compartments air from the outside. This will be accomplished because some of the air lying over or near the first exhaust ports will receive by contact from the exaust gas issuing from these orts a degree of the forward motion. Moving away with exhaust gases, the space formerly occupied by this air will be taken by the air lying nearest it. resulting in the forward movement of all the air occupying a space from the first series of ports to the several entrances of the passages, and resulting finally in steady streams of air flowing into these passages, developing on their own account centrifugal force operative over the first series of ports increasing, because of a lessening atmospheric pressure on these orts, the amount of gas issuing from them.

t follows, then, that the greater the speed or rate of the original discharged gases. the greater will be the rate of progress of these gases through the passages, the greater their rate of rotation, the greater the centrifugal force operating as a suction upon the axial center ofthe system, and upon the exhaust ports. The result will be a free escape of exhaust gases and a practical elimination of,

back pressure.

If however, the apparatus is so placed upon amoving object as to receive upon its forward end'the pressure of air as it moves into it, then this air impelled into the spiral passages and forced by them to revolve about the inner or exhaust tube, will develop, independently of any action the gases "from exhaust ports may exert, a centrifugal original impulse as it progresses along the inner tube will exhaust progressively through the ports as 1t passes over them,

thus each original impulse will be broken up into a series of minor impulses and those from the first original impulse, because of the greater length they are made to travel in the spiral passages, will be retarded and mixed with those from the second impulse or even the third.

It is obvious that if the original impulses are rapid, this intermingling is facilitated and that by timing spacing and shaping of ports, the impulses may be so mixed. that no matter what the frequency or strength of original impulses, they may be broken up and mixed one with another so as to produce a substantially steady flow of released gas, producing'no major sound vibrations or accents, and permitting a silent exhaust.

It is diflicult within the prescribed limits of a single application to set forth the many possible modifications which may be made in the form of device shown without de parture from the invention. Nor do I go more specifically into. the details of construction of the device now under consideration 'as these are largely immaterial. It may, however, be stated that the partitions C are so formed that at the lines of union with the exhaust pipe B their surfaces approximate planes parallel to the paths of the gases issuing from the ports. and are soformed in other respects as to lead the gases outward with the least resistance.

The outer shell should extend practically to the end, though it may be beyond the ends of the spiral compartments, and at the smaller end it may be continued slightly beyond the point of the beginning of such compartments.

I may use any suitable means for attaching or detaching the outer casing, but this and other details are within the province of the expert and require no specific description.

What I claim is ,7

1. In a muffler for internal combustion engines, the combination with an exhaust pipe having a series of ports along the same, of a surroundin means for producmg a rotary flow of air or gas in a spiral path in and through the same which by centrifugal action will reduce the atmospheric pressure below the normal at the center thereof and at the exhaust ports.

2. In a mufiier for internal combustion engines, the combination with an exhaust pipe having a series of exhaust openings or ports along the same, of a plurality of spiral chambers or compartments inclosing the said pipe and into which the ports open, and means for producing through said compartments a flow of air or gas which will have a ports therein.

rotary motion with reference to the exhaust pipe'and thereby reduce by its centrlfugal action the atmospheric pressure below the normal around the exhaust pipe and at the 3. In a mufiler for internal combustion engines, the combination with an exhaust pipe having. a series of ports along the same, of a casing surrounding the same d1- vided into a plurality of spiral compartments radually enlarged toward their outlet en s, and into which the exhaust ports open, whereby there is generated and maintained a flow of air or gas by the force of the discharge from said 'exhaust ports through the compartments and having a ro- Y tary motion with reference to the exhaust pipe to reduce the atmospheric pressure below the normal at said ports.

4. In a muffler for internal combustion engines, the combination with a perforated exhaust pipe of a casing surrounding the same, partitions therein forming a plurality of spiral compartments open at both ends and gradually enlarged toward the outlet for the purpose set forth.

5. In a mufiler for internal combustion inclosing chamber, and r engines, the combination with a perforated exhaust pipe, of a casing surrounding the same having a slightly flared open entrance end and gradually enlarged toward the outlet end, and partitions therein forming a plurality of gradually enlarged spiral compartmentsaround the ,exhaust pipe as and for the purpose set forth.

6. In a muflier for internal combustion engines, the combination of a vconical exhaust fpipe with perforations therein, a casing 0 corresponding contour surrounding the same and having both ends open, and

partitions within the space between the exto flow with a rotary motion around the said pipe and long passages for the escaping exhaust gas are provided.

8. A muffler for internal combustion engines, comprising in combination, an exhaust pipe with exhaust ports therein, a casing surrounding said pipe throughwhich a flow of air or gas is inducedby the disgines, the combination with an exhaust pipe charged exhaust impulses in a rotary'direcvtion with respect to the said exhaust pipe,

and passages for the exhaust gases of a length suflicient to mix and mufile the sound impulses as set forth.

9. In a mufiier for internal combustion engines, the combination with .achamber formed or provided with means for producing a rotary flow of air or gas in and completely through the same which, by centrifugal action, will reduce the atmospheric pressure at the central portion of the same, of exhaust ports opening into said central portion of the chamber and discharging therein in such manner as to set up and maintain such rotary flow.

In testimony whereof I hereunto aflix my signature.

' HAMILTON GIBSON. 

